Sex differences in the strategies used by rats to solve a navigation task.

Rats were trained in a triangular-shaped pool to find a hidden platform, whose location was defined in terms of two sources of information, a landmark outside the pool and a particular corner of the pool. Subsequent test trials without the platform pitted these two sources of information against one another. This test revealed a clear sex difference. Females spent more time in an area of the pool that corresponded to the landmark, whereas males spent more time in the distinctive corner of the pool even though further tests revealed that both sexes had learned about the two sources of information by presenting cues individually. The results agree with the claim that males and females use different types of information in spatial navigation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Complete suppression to a compound CS does not block further conditioning to each element.

In 2 of 3 experiments studying conditioned suppression, 54 male hooded rats were initially given a small number of tone-shock and light-shock trials sufficient to produce complete suppression to the tone-light compound. According to a model proposed by R. A. Rescorla and A. R. Wagner in 1972, if a compound conditioned stimulus produces asymptotic suppression, no further conditioning will occur to either element when further reinforced trials are given with the compound. Although R. A. Rescorla has reported some evidence supporting this prediction, in both the present experiments Ss given further reinforced training with the tone-light compound showed significant increments in conditioning to each element. In the 3rd experiment 24 male hooded rats were given a larger number of noise-shock and light-shock trials, followed by reinforced noise-light compound trials. Additional reinforcement of the compound did not lead to a change in the associative strength of each element, although the model proposed by Rescorla and Wagner predicts that associative strength should decrease following such training. (French summary) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Exploring 17α-ethinylestradiol removal, mineralization, and bioincorporation in engineered bioreactors

This research investigated removal, mineralization, and bioincorporation of 17α-ethinylestradiol (EE₂) in membrane bioreactors and conventional bioreactors. When the influent EE₂ concentration was >50 μg/L, the membrane bioreactor (MBR) biomass removed more EE₂ than conventional bioreactor (CBR) biomass in continuous tests, likely because the sorption partitioning coefficients are higher for MBR biomass. Microautoradiography was carried out to investigate the distribution of EE₂ within the aggregates retrieved from the bioreactors, and the results revealed concentration gradients present within the floc. Experiments using radiolabeled ¹⁴C-EE₂ experiments (done with 24.5 μg/L EE₂) showed that EE₂ removal rates and the amount of EE₂ mineralized were similar in MBRs and CBRs. Direct measurements and bioenergetic estimates suggest that EE₂-related carbon is probably incorporated into active biomass, despite the fact that EE₂ was added at a concentration that was much lower than that of the primary growth substrates.     

Isolation from an ant Myrmecia gulosa of two inducible O-glycosylated proline-rich antibacterial peptides

Reported here is the isolation and characterization of two antibacterial peptides synthesized in an ant Myrmecia gulosa in response to bacterial challenge. The peptides were purified by reversed-phase high performance liquid chromatography and characterized by peptide sequencing and mass spectrometry. Both peptides were formed from 16 amino acids, were rich in proline ( approximately 30%), and had N-acetylgalactosamine O-linked to a conserved threonine. The activity of a synthetic non-glycosylated isoform was markedly reduced demonstrating that glycosylation was necessary for maximum activity. The peptides were active only against growing Escherichia coli. They were inactive against stationary cells, Gram-positive bacteria, the yeast Candida albicans, two species of mammalian cells, and bovine pestivirus.     

Induced emotional interpretation bias and anxiety.

Five experiments are reported showing that the interpretation of personally relevant emotional information can be modified by systematic exposure to congruent exemplars. Participants were induced to interpret ambiguous information in a relatively threatening or a benign way. Comparison with a baseline condition suggested that negative and positive induction had similar but opposing effects. Induction of an interpretative bias did not require active generation of personally relevant meanings, but such active processing was necessary before state anxiety changed in parallel with the induced interpretative bias. These findings provide evidence consistent with a causal link between the deployment of interpretative bias and anxiety and reveal something of the processes underlying this association. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Simultaneous activation of the representations of absent cues results in the formation of an excitatory association between them.

It is a common assumption of associative theories of learning that no change in the strength of an associative connection between 2 cues is possible in the absence of those cues. However, recently suggested modifications to associative theory (A. Dickinson & J., Burke 1996) have questioned this assumption by arguing that if the representations of 2 cues are simultaneously retrieved from memory, an association will be formed between them even though the cues themselves are not present. A flavor preference procedure was used to find evidence for such associations. In 3 experiments a novel excitatory connection was formed between the representations of peppermint and sucrose in their absence. This suggests that the assumption that cues cannot undergo a change of associative strength in their absence should be abandoned. The tension between the current results and accounts of mediated conditioning is discussed, and some suggestions regarding the difference between the 2 procedures are proposed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Late, intermittent obstruction of a mitral prosthesis by chordal remnants

A 59 year old male was admitted 10 weeks following insertion of a Medtronic Hall mitral prosthesis. He suffered recurrent episodes of electromechanical dissociation (EMD). Transthoracic echocardiography demonstrated that during the times of haemodynamic compromise, the mitral prosthesis was intermittently obstructed. Emergency surgical intervention revealed that chordae tendineae had prolapsed through the lesser orifice, obstructing the valve mechanism. The mitral remnants were excised, and as the valve functioned normally, it was not replaced. Postoperatively, the patient made an uneventful recovery. This case illustrates the Doppler echocardiographic features associated with extrinsic obstruction of a mitral prosthesis, and demonstrates that this unusual complication can be responsible for late valve dysfunction.     

Selective attention in animal discrimination learning.

2 classes of experiment on the role of attention in discrimination learning are reviewed: (a) Investigations of the effect of attention on the amount learned about different cues have been interpreted as disproving noncontinuity theory (according to which animals attend to only 1 cue at a time). The fact that animals learn something about a 2nd cue, however, does not prove that attention has no effect on learning, and more recent evidence shows that it does. (b) If animals do not automatically attend to all cues, part of what they must learn in order to solve a discrimination problem is to attend to the relevant cue. Experiments on the acquired distinctiveness of cues, transfer along a continuum, and reversal learning provide evidence for the importance of such classificatory learning. (155 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Charge generation in TRAPATT diodes

The charge generated during an avalanche in a TRAPATT diode is shown to be proportional to the current at the instant of triggering. The constant-current frequency is shown to be an important diode parameter.